//leetcode 526 优美的排列
public class Test1 {
    int ret;
    boolean[] check;
    public int countArrangement(int n) {
        check = new boolean[n + 1];
        dfs(1, n);
        return ret;
    }

    private void dfs(int pos, int n) {
        if (pos == n + 1) {
            ret++;
            return;
        }
        for (int i = 1; i <= n; i++) {
            if (!check[i] && (pos % i == 0 || i % pos == 0)) {
                check[i] = true;
                dfs(pos + 1, n);
                check[i] = false;
            }
        }
    }
}
